It is well known that polyamides such as nylon-5, nylon-6, nylon-8, and nylon-12 have been produced by ring-opening polymerization of appropriate lactams. Nylon-6, also called polycaprolactam, was originated by I. G. Farbenindustrie in 1940. In one preparation technique, the polymerization of .epsilon.-caprolactam (also known as .epsilon.-aminocaprolactam or simply caprolactam), is carried out by adding water to open the ring and then removing water again at elevated temperature, where linear polymer forms. Caprolactam may also be polymerized by ionic chain mechanisms.
Nylon-6 has properties similar to nylon-66, but has a lower crystalline melting point and is somewhat softer and less stiff. The major use for the polymer is in tire cord. Polycaprolactam accounts for about 25% of U.S. consumption of nylon.
Methods are constantly being sought for the improvement of these polymers. For example, a few years after the invention of nylon 6,6 made from hexamethylene diamine and adipic acid, it was discovered that substitution of a portion of hexamethylene diamine with triethyleneglycol diamine gave polyamides with better dye receptivity and enhanced water absorption. An excellent example of how comfort and feel can be added to nylon 6 type polyamides has been described by R. A. Lofquist, et al., "Hydrophilic Nylon for Improved Apparel Comfort," Textile Research Journal, June 1985, p. 325-333. These authors copolymerized caprolactam with polyethyleneoxy diamines and dibasic acids such as terephthalic acid. Comfort-related tests revealed that fabrics made from such fibers are superior to those from polyesters and polyamides. See also U.S. Pat. No. 4,919,997 for a description of water-absorbing mats made using these techniques. The melt-blown water-absorbing mat of fibers of this patent comprise a block copolyether-amide having polyether and polyamide segments. The JEFFAMINE.RTM. ED-Series amines were used as the amine-terminated polyethylene oxide glycols by Lofquist, et al. to produce a modified nylon-6. These amines are high molecular weight (600 to 2000) alkylene glycol diamines having the formula H.sub.2 NRNH.sub.2, where the radical R is a polyoxyalkylene chain of molecular weight from about 200 to about 4000 having terminal carbon atoms to which nitrogen atoms are bonded. Moisture absorption was found to be greatest using the amines having the highest molecular weight.
U.S. Pat. No. 3,454,534 indicates that the hydrophilic characteristics of nylon-66 may be improved by adding a polyalkylene glycol diamine to the molten polymer prior to spinning. The process involves producing polyhexamethylene adipamide where equimolar proportions of adipic acid and hexamethylene diamine are reacted together to form molten polyhexamethylene adipamide. The improvement involved introducing from about 0.3 to 3.0 weight percent of a polyalkylene glycol diamine into the molten polymer subsequent to polymer formation and prior to spinning. The polyalkylene glycol diamine has the formula: H.sub.2 N--(CH.sub.2).sub.3 --O--[R--O].sub.x --(CH.sub.2).sub.3 --NH.sub.2 where R is an alkylene hydrocarbon radical having a chain length of from 2 to about 8 carbon atoms, and x is an integer sufficiently large to confer a molecular weight of at least 1000. Note that propylene linkages are required and that the polyalkylene glycol diamine must have a molecular weight of at least 1000.
The U.S. Pat. No. 4,017,557 teaches 6-nylons and 12-nylons having primary amino end-groups and an average degree of polymerization of about 5-60 may be grafted onto elastomeric trunk polymers having anhydride groups, vicinal carboxylic groups, or carboxylic groups adjacent to alkoxycarbonyl groups by heating a mixture of the nylon and the trunk polymer, preferably under high shear conditions for about 1 minute or less to 30 minutes or more above the melting temperature of the nylon. The resulting elastomeric graft polymers are suitable for fabricating into a variety of articles, such as, for example, wire jacketing, hose, belts, seals, gaskets, and low pressure tires.
It is known to use monoamines and diamines to effect the polymerization of caprolactam. These amines do not contain ether groups and are taught as initiators and not as reactive modifiers. See, for example, T. G. Majury, "Amines and Carboxylic Acids as Initiators of Polymerization in Caprolactam," Journal of Polymer Science, Vol. 31, 1958, pp. 383-397, which concerns the polymerization of caprolactam with amines and carboxylic acids. The author concluded that acids induce more rapid polymerization than bases.
I. A. Tutorskii, et al. in "Interaction of Carboxyl-Containing Butadiene-Styrene Rubbers with Polyamides and .epsilon.-Caprolactam," Journal of Polymer Science, Vol. 61, 1962, pp. 97-108, report grafting of caprolactam onto carboxylated butadiene-styrene rubbers by heating the rubber and the lactam in the presence of boron trifluoride. C. B. Chapman, et al. in "The Preparation and Properties of Grafts of Polycaprolactam on Vinyl Copolymers," Journal of Polymer Science, Vol. 34, 1959, pp. 319-335, describe the polymerization of caprolactam at elevated temperatures in the presence of a copolymer of styrene with acrylic acid or maleic anhydride. Gelling was observed in several instances.
Although polyamides have been incrementally improved as shown by the publications discussed above as examples, there remains a need for new polyamides having improved properties. For example, in contrast to the Chapman, et al. article, preferably copolymers with cyclic lactams would not gel. In particular, it is always desirable to produce engineering plastics, fibers or adhesives with new properties so that new uses may be explored.